Hypochlorite sweetening process



May 1, 1951 n. cqBANDoN TAL 2,550,668

HYPOCHLORITE SWEE'VIENING PROCESS Filed April 8, 1949 Patented May 1`, 1951 UNITED STATES HYPOCHLORITE SWEETENING PROCESS Richard C. Brandon, Elizabeth, and'Minor C. K.

Jones, Monntainside, N. J., assignors to Standard Oil Development Company, a corporation of Delaware Application April s, 1949; serial No. 86,152

more particularly concerned with the removal Aof mer-captan' compounds,r particularly those mercaptan` compounds which have heretofore been relatively diflicult to remove from hydrocarbon fractions, especially from those fractions boiling in the motor fuel, kerosene, Diesel oil and heatingoil boiling ranges. In accordancewith the presentinvention a feed hydrocarbon oil char-V acterized by containing mercaptan compounds is contacted with` a hypochlorite treating solution which is characterized by containing a high concentration lof free hydroxide.

In accordance with a preferred adaptation of the present invention an uncracked feed hydrocarbonstream is treated with a hypochlorite solution of this character under conditions whereby unexpected and desirable results are secured. A particular embodiment of the present' invention comprises treating a prime cut hydrocarbon fraction, especiallya fraction boiling in the kerosene boiling range, (350 to 550 F.) with a hypochlorite solution which is characterized by containing a high concentration of free hydroxide anda-high concentration of a chloridesalt.

It is well known in the art to treat petroleum oils by various procedures in order to remove objectionable compounds, as for example,'sulfur compounds therefrom.v` For example, it is known to treat petroleum fractions boiling in the'motor fuel boiling range and in the general range below `about 700 F. with various chemical reagents such as sodiumorpotassium hydroxide solutions. It is also known to treat sulfur-containing feed oils with a so-called, Doctor treat wherein the oil is contacted with a lead oxide solution in the presence of free sulfur. This treatment `convertsthe objectionable mercaptan compounds to relatively innocuous alkyl disulphides.

It has also been suggested that objectionable mercaptan compounds be removed 'fror'n hydro- Y carbon fractions particularly those boiling below -f `means of line 6 and is preferably recycled to The mercaptans present about 700 F. by treating the same with a' hypochlorite solution, as for example, with sodium or calcium hypochlorite.

tans to disulphides. Furthermore, as pointed out heretofore, sodium hydroxide per Vse will not function to remove satisfactorily the mercaptans,`

particularly the higherf boiling mercaptans, from' Y thefoil containing thesame.A l

It has rnow'been discovered, however, thatif the hypochlorite solution contains a relatively high concentration of free hydroxide, as forexample, sodium hydroxide, unexpected and desir-f ableresults will be secured. It has also further been discovered that if the hypochlorite solution containing arelatively high concentration of hydroxide also vcontains a relatively high con-l centration of a chloride salt, as for example sodium chloride, still further desirable results are secured.

The present invention may be readily under- .stood'byv reference to the drawing illustrating one embodiment of the same. Referring specically to `the* drawingva feed oil, which for the purpose of-^ill-ustration`is assumed to be a kerosenev boiling intthev range froml about 340 F. to

530 F. and which contains mercaptans is introduced into the system by means of feed line l. In accordance with one ladaptation of the invention., a hypochlorite solution which for the purpose of illustration is assumed to be a sodium hypochlorite solutiomand which contains a `high concentration of an alkali hydroxide, as for exampleV sodium hydroxide, isY introduced into line I by means of line 2. These streams are mixed" in 'mixing zone'3 and then introduced into rerun in a distillation operation.

react'fwith hypochlorite solution to form'alkyl the hypochlorite solution.k Relatively high concentrations of hydroxide have been avoidedk since it was felt that the presence -of the `hy'fd'roxide tendedto impair the conversionofvthemercapa settling zone 45 It is to be understood that settling zone d may comprise'any suitable number and arrangement of settling stages. A treated oil Vfree of mercaptans is withdrawn from zone 4 by means of line 5. This oil may be further refinediorr handled in' any manner desirable.V Generally, this oilY is washed with a relatively strong* caustic solution, as for example, a sodium hydroxide solution, or it may be clay filtered or The hypochlorite solution is withdrawn from zone 4 by line l. "In a continuous operation a portion of the spent treating solution may be withdrawn from'the system by means of line 1 and handled as desired.

acne Sis adjusted so that the resulting hypol chlorite 'solution'contains a relatively high concentration of free sodiumfhydroxide. This solu` tion is -then introducedinto line? by means of line ll and mixed with the oilaspreviously'da 3 scribed. In accordance with a preferred adaptation of the invention additional chloride as for example, sodium chloride, is introduced into the hypochlorite solution in zone 8 by means of line I2.

The present invention is broadly concerned with the removal of mercaptans from hydrocarbon fractions boiling below about '700 F. It is particularly directed toward the removal of mercaptan compounds from uncracked hydrocarbon fractions, especially those fractionsboiling in the range from about 300 F. to 600 F. In aocordance with the present invention, a hypochlorite solution containing a relatively high concentration of free hydroxide is employed. The hypochlorite solution is preferably a sodium orlithium hypochlorite solution. However, any alkali metal or alkali earth metal may be used. Suitable metals for example are lithium, potassium, calcium, barium and strontium.

The amount of hypochlorite solution employed may vary appreciably, as for example, from about to 50% and higher of the hypochlorite solution based upon the volume of oil being treated. However, in general it is desired to maintain the quantity of treating solution as low as possible. This is essential since the hypochlorite solution is a relatively strong oxidizing agent and if an excess of oxygen be present, various side reactions ocour other than the formation of the disulphides from the mercaptans. One side reaction which occurs is that oil-soluble sulfonic acids are formed. Also, sulfonyl chlorides are formed if too great a quantity of hypochlorite solution be utilized. Another reaction which occurs is the formation of sulfones from thioethers which may be present in the feed oil. These undesirable compounds tend to decompose upon further refining of the oil resulting in the formation of acidic constituents as for example hydrogen chloride and sulfur dioxide.

In accordance with the process of the present invention it is therefore desirable that the oil be treated with not greater than 20% by Voltune of the hypochlorite solution. In general it is preferred that the quantity of hypochlorite solution employed be less than about 10%, preferably in the range from about 2 to 5% of hypochlorite solution based upon the oil being treated.

The concentration of the hypochlorite solution likewise may vary appreciably and will be a function to some extent of the amount of solution utilized. However, in general it is preferred that the concentration of the hypochlorite solution be The amount of free sodium hydroxide present may vary appreciably but in accordance with the present ,invention it is preferred that not less than about 50 grams per liter of treating solution and preferably from 100 to 300 grams per liter of free sodium hydroxide be present. If sodium chloride be used in conjunction with the free sodium hydroxide and the hypochlorite solution, it is preferred that from about 50 to 200 grams per liter of sodium chloride or equivalent be utilized based upon the treating solution.

The time of contact may be varied appreciably depending upon other operating conditions, however, in general it is preferred to have the time of contact not in excess of about 10 minutes. Desirable times of contact are in the range from about 2 to 5 minutes.

The present invention -may be more fully understood by the following examples illustrating the same.

EXAMPLEv 1 A hydrocarbon fraction boiling in the range from about 100 F. to 320 F. and secured from a catalytic cracking operation had a ASTM gum1 of 3 and an ASTM breakdown 2 of 340. This oil was treated with 50% by volume of a hypochlorite solution containing 10.7 grams per liter of sodium hypochlorite and 2 grams per liter of sodium hydroxide. The resulting product had a gum content of l2 and a breakdown of 160.

EXAlWPLE 2 An operation was conducted similar to that described with respect to Example 1 except that the feed oil was a cracked oil boiling in the range from about 100 F. to 430 F. The feed oil had an ASTM gum content of 19 and an ASTM breakdown of 360. The treated product had an ASTM gum content of 28 and an ASTM breakdown of r200.

From the above two examples, it is apparent that the hypochlorite solution of the present invention is not particularly adapted to the treatment of cracked oils.

EXAMPLE 3 An uncracked kerosene fraction containing mercaptans and boiling in the range from about 340 to 530 F. was contacted with various hypochlorite solutions for contact times of about 2 minutes.

The results of these operations are listed as follows:

Eect of excess sodium hydroxide in hypochlorite sweetemng of Iraq kerosene in two minutes Contact time not in excess of about grams of sodium hypochlorite or equivalent per liter and preferably be in the range from about 2 to l2 grams 4per liter of treating solution.

These results show that the kerosene can be sweetened with progressively smaller amounts njssiillgrams of gum per milliliters, ASTMV Test 1-36, Gum Content of Gasoline (Air-jet methodL 1 ASTM Designation D-525-46.

i frs-50,60s S 6 of hypochlori'teas excess sodium'hydroxide is eXCeSSvS'dum'hydroxideffisaemployedpiand .also

. increasd ,from 2 ,150; 51 g./1 when a4 relatively .lowcvolumerofaztreatcis utilized.

From the above it is apparentethatvery de- ',EXAMPLEjG;

sirable resultsf are secured by utilizing a hyno- 5 Additinaiopemi-ionswereconducted wherein chlorite z solution containingzaa relatively high an excessof sodium chloridewas Aged in mn.

.cnntmtion of..sodium..hydr0xide .junction/with .an xcess of sodium .hydroxide Theresults of .these .operations v:are pas :follows:

Effectief excessodiumfchloride im hypochlorz'te sweetem'ng oflraq kerosene 7(14 fmy. mercaptan sulfur/100 mZ.)

DNP...

1 Amounts of sodium chloride shown were weighed into the solutions; NaOH and N aOCl were determined by analysis.

EXAMPLE 4 From the above it is readily apparent that when An uncracked kerosene secured from a West excess sodium chloride is used in conjunction with Texas crude and boiling in the range from about'l a ,hypochlorlte Solutlol Whlch Con'alns a re1- 350 to 530 F- which contained 99 milligrams of 30 atively 10W concentration of sodium hydroxide, mercaptan sulfur per 100 milliliters was treated 110 marked effect iS Secured. However, when exin various operations with the following results. cess sodium chloride is used in conjunction with EJect of excess sodium hydroxide in hypochlorzte Swcetemng of West Texas kerosene in two minutes contact time From the above data it is apparent that for a a hypochlorite solution which has a high coniixed NaOH concentration, as the quantity of centration of sodium hydroxide, unexpected and treat increased the tendency to form undesirable 50 desirable results are secured.

sulfonic acids and sulfonyl chlorides increased A Very specific embodiment of the present inprohibitively as evidenced by the increase in vention is to remove mercaptans from oils conacidity. On the other hand, in operation 5, taining the same utilizing ahypochlorite solution wherein an excess of sodium hydroxide was emas described and to Contact the treated oil in a ployed, the acidity was appreciably lower. 55 subsequent stage with tetraethanol ammonium EXAMPLE 5 hydroxide. A preferred concentration is to use i from 15 to 25% aqueous solution of tetraethanol Other operations were conducted using an unammonium hydroxide. In an operation wherein cracked kerosene, secured from an Iraq crude, a 20% solution of tetraethanol ammonium hyand boiling in the range from 350 to 500 F. with 60 droxide Was employed it was found that the the following results: Weight per cent of chlorine remaining in the oil Iraq kerosene It is apparent from the above that excellent was reduced to about one-iteenth of the chloresults are secured when the amount of rine content of the oil which was not so treated. hypochlorite is maintained relatively low, when Having described the invention it is claimed:

Proce'ss fo'r the removal of inercaptan cornaounds from a petroleum oil containing mercaptan compounds which comprises contacting said petroleum oil with an alkali hypochlorite solution which is characterized by containing about 2 to 10 grams per liter of the said alkali hypochlorite, said solution further containing about 50 to 250 grams per liter of alkali hydroxide, and said solution further containing about 50 to 200 grams per liter of an alkali metal chloride salt.

2. The process defined by claim 1 wherein the said petroleum oil boils below about 700 F.

3. The process Ydeiined by claim 1 wherein the said alkali constitutes sodium.

RICHARD C. BRANDON.

MINOR C. K. JONES.

REFERENCES CITED The following references are of record in th le of this patent:

UNITED STATES PATENTS Number Name Date 723,368 Amend Mar. 24, 1903 2,438,018 Nixon et al Mar. 16, 1948 2,488,855 Denton Nov. 22, 1949 FOREIGN PATENTS Number Country Date 288,931 Great Britain Apr. 13, 1928 OTHER REFERENCES WOOd et a1., Ind. 8: Eng. Chem., 18, 823 t0 826. 

1. PROCESS FOR THE REMOVAL OF MERCAPTAN COMPOUNDS FROM A PETROLEUM OIL CONTAINING MERCAPTAN COMPOUNDS WHICH COMPRISES CONTACTING SAID PETROLEUM OIL WITH AN ALKALI HYPOCHLORITE SOLUTION WHICH IS CHARACTERIZED BY CONTAINING ABOUT 2 TO 10 GRAMS PER LITER OF THE SAID ALKALI HYPOCHLORITE, SAID SOLUTION FURTHER CONTAINING ABOUT 50 TO 250 GRAMS PER LITER OF ALKALI HYDROXIDE, AND 